1. Field of the Invention
The present invention relates to valve position indicators for fuel injector valves, and more particularly, to a valve position sensor which generates an electrical signal which corresponds to the movement of a poppet valve within a fuel injector.
2. Description of the Prior Art
A needle valve within a fuel injector nozzle holder is opened and closed at appropriately timed intervals to inject desired amounts of fuel into a cylinder of an internal combustion engine such as a diesel engine. It is essential to know when the needle valve opens in relation to the engine crank shaft position in order to designate the appropriate engine timing.
The needle valve comprises a needle and a needle seat. When the needle contacts the needle seat, the valve is closed. When the needle is lifted off the needle seat, the valve opens and fuel is metered through spray orifices into the interior of the engine cylinder. The initial relative vertical displacement between the needle and the needle seat determines the beginning of injection as well as the engine timing.
A poppet fuel injector valve is a related type of fuel injection device which includes an outwardly opening poppet valve for metering fuel through a circular orifice into the interior of an engine cylinder. This type of fuel injector valve includes a spring which biases the poppet valve into the closed position.
Engine timing must be set with precision to not only properly operate the engine, but also to control fuel consumption and the production of undesirable emissions. The engine timing must be set precisely for low fuel consumption while simultaneously minimizing undesired engine emissions. Since there is always a trade off between optimizing fuel consumption and minimizing emissions, engine timing must be set at a point which somewhat compromises both fuel consumption and emission reduction. As a result of the extremely stringent government fuel consumption and emission regulations, the engine timing must be optimized to levels substantially in excess of any prior art requirements. Conventionally, engine timing has been determined by reference to visual markings on the engine flywheel. Robert Bosch has recently exhibited a fuel injector nozzle holder equipped with a non-removable built-in inductive sensor for measuring the engine timing. Capacitive and other methods of measuring needle lift have been used experimentally in the laboratory.
The Creative Tool Company of Lyons, Illinois, is presently selling a product designated as a DIESEL TACH-TIME CT4000 instrument. This product utilizes a split-nut transducer which is installed on an engine cylinder fuel line at either the fuel injection pump or at the nozzle. The mechanical strains produced by the transit of a fuel pressure pulse through the fuel line create mechanical displacements of the fuel line and cause mechanical displacements of the split-nut transducer. When this transducer is deformed, an electrical impulse is sent to the tachometer-timing light unit. This device thereby provides a method of dynamically determining fuel injection pump timing.